如何使用R从字符串中删除所有数字和逗号（除了任何紧跟$的数字）？

Question

I would like to remove all numbers and commas from a string except any number that is immediately preceded by $ and immediately followed by a comma.

For example, I have:

str = "1, $100-$1,000 2, $1001-$10,000 3, $10,001-$100,000"

I would like to obtain the following:

"$100-$1,000  $1001-$10,000  $10,001-$100,000"

I have tried to use gsub with a negative lookbehind

new_str = gsub("(?<!\\$)[0-9]*,", "", str)

However, this gives the following error message:

Error in gsub("(?<!\\$)[0-9]*,", "", str) : invalid regular expression '(<!\$)[0-9]*,', reason 'Invalid regexp'

It seems that the negative lookbehind is incorrectly coded, but I can't seem to figure out why. Any help is much appreciated!

Answer 1

1) This gives the desired answer in the case of the sample string:

gsub("\\d+, ", "", str)
## [1] "$100-$1,000 $1001-$10,000 $10,001-$100,000"

Visualization of regular expression

\d+, 

Debuggex Demo

2) Here is a second approach:

library(gsubfn)

paste(strapplyc(str, "(\\$\\S+)", simplify = c), collapse = " ")
## [1] "$100-$1,000 $1001-$10,000 $10,001-$100,000"

Visualization of regular expression

(\$\S+)

Debuggex Demo

Answer 2

you could use this pattern

(\$[0-9,-]+)|\d+,\s 

and replace w/ \\1
Demo